A machine for producing packaging is intended for the manufacture of boxes which form the packaging, after folding and gluing. In the machine, an initial flat substrate, such as a continuous web of cardboard, is unwound and is printed by a print unit, made up by printing units. The web is then transferred into a converting unit, in order to make plate elements, in this case boxes.
The converting unit comprises at least one converting arrangement provided with two cylindrical rotary tools, positioned parallel to one another and spaced apart with respect to the diameter of the tools, so as to cooperate. The web runs in a gap between the two tools in order to be converted there. Each of the two tools turns in a respective opposite direction. The first tool is rotatably mounted in a first and a second bearing and the second tool is rotatably mounted in a third and a fourth bearing. The first and third and also the second and fourth bearings are spaced apart with respect to the diameter of the tools. Tightening elements are provided in order to maintain the first and the third bearing as well as the second and the fourth bearing firmly together. Most of the time, the converting arrangement is provided so as to form a cassette. The cassette is inserted by sliding it into each of the lateral supporting frames of the unit.
The cassette allows the tools to be changed quickly, in terms of the conversions of the substrate to be realized. The packaging manufacturer has at least two cassettes. A first cassette is in the machine currently operating and has been adapted in terms of the current converting job. During this time, a second cassette may be being assembled and adjusted so as to be adapted for the following converting job. When the job is to be changed, the operator takes out the old cassette and inserts the new cassette, reducing the time the machine is stopped to a minimum.
As a first example, one of the arrangements or one of the cassettes is a rotary cutting arrangement or a rotary cutting cassette respectively. A first cylindrical cutting tool is provided with knives, and a second cylindrical tool is smooth and is called an anvil. At the moment of the cut, the edges of the knives of the cutting tool must pass as close as possible to the anvil cylinder so as to carry out a clean cut. The edges of the knives, however, must not touch the anvil cylinder as they would be irreparably destroyed during rotation. The constituent material of the support, i.e. the fibers in the case of cardboard, must not appear or be visible at the cut. Neither is it desirable to have dust originating from the cut in the constituent material of the support.
This is why the optimum radial gap between the two cylindrical rotary tools is adjusted to a micron degree. So that said gap is obtained in such a precise manner, each end of the two cylindrical rotary tools comprises a bearing ring around a respective tool. The bearing ring at one end of one of the tools rolls on the bearing ring at the same end of the other of the tools (see document EP-0,764,505).
As a second example, one of the arrangements or one of the cassettes is a rotary creasing arrangement or a rotary creasing cassette respectively. A first cylindrical creasing tool is provided with a male creasing form or matrix and a second cylindrical tool is provided with a complementary female creasing form or matrix. The creasing must be clean, with no fractures on the edges or the bottom of the creasing. In this case, the optimum radial gap between the two cylindrical rotary tools is adjusted to the hundredth of a millimeter.